A two-switch circuit topology typically includes a pair of switching devices that are alternately operated. For example, a power inverter can include one or more branches coupled to a DC power source. Each branch can include a pair of switching devices that are alternately operated to connect the junction between the devices to the voltage of the power source, thereby producing an alternating output. Shoot-through currents can occur if both switching devices are turned on at the same time, which can damage and/or short circuit components of the circuit and degrade the output waveform.
One method for minimizing shoot-thorough phenomenon involves the use of an interlock circuit to prevent both switching devices from being on simultaneously. Interlock circuits typically regulate switching based on a signal sensed from one of the inputs to the switching devices. For example, FIG. 1 illustrates a shoot-through protection circuit diagram using an upper interlock circuit, which is configured to turn off the lower gate driver if a signal sensed at the gate/base of the upper switching device exceeds a certain threshold. However, interlock circuits do not consider noise factors that can exist in real-world applications such as when noise is coupled into the gate of the switching devices.
Another method for shoot-thorough protection involves the use of an anti-saturation circuit, which controls the switching device based on the measured voltage across the switching device. FIG. 2 illustrates a shoot-through protection circuit diagram using anti-saturation circuits. Each anti-saturation circuit monitors the voltage on an output terminal of a switching device—such as the drain-source terminals of a field-effect transistor (FET) or the collector-emitter terminals of a bipolar junction transistor (BJT). If the measured voltage indicates that the switching devices is entering or operating in an active or linear condition, then the anti-saturation circuit can adjust the respective driver of the gate/base to turn the switching device off. However, anti-saturation circuits can prematurely turn off the switching device due to its sensitivity.